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#!/usr/bin/env python
"""
Create irregular mesh on a regular tetrahedron centered at the origin.
"""
import meshpy.tet
import numpy as np
def create_tetrahedron_mesh(maxvol=0.1):
# circumcircle radius
r = 5.0
# boundary points
points = []
points.append((0.0, 0.0, r))
# theta = arccos(-1/3) (tetrahedral angle)
costheta = -1.0 / 3.0
sintheta = 2.0 / 3.0 * np.sqrt(2.0)
# phi = 0.0
sinphi = 0.0
cosphi = 1.0
points.append((r * cosphi * sintheta, r * sinphi * sintheta, r * costheta))
# phi = np.pi * 2.0 / 3.0
sinphi = np.sqrt(3.0) / 2.0
cosphi = -0.5
points.append((r * cosphi * sintheta, r * sinphi * sintheta, r * costheta))
# phi = - np.pi * 2.0 / 3.0
sinphi = -np.sqrt(3.0) / 2.0
cosphi = -0.5
points.append((r * cosphi * sintheta, r * sinphi * sintheta, r * costheta))
# boundary faces
facets = [[0, 1, 2], [0, 2, 3], [0, 3, 1], [1, 2, 3]]
# create the mesh
# Set the geometry and build the mesh.
info = meshpy.tet.MeshInfo()
info.set_points(points)
info.set_facets(facets)
meshpy_mesh = meshpy.tet.build(info, max_volume=maxvol)
return np.array(meshpy_mesh.points), np.array(meshpy_mesh.elements)
if __name__ == "__main__":
import meshio
points, cells = create_tetrahedron_mesh(10.0)
meshio.write("tetrahedron.vtu", points, {"tetra": cells})
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